Checkbox plugin

This plugin renders checkbox icons in front of each node, making multiple selection much easier. It also supports tri-state behavior, meaning that if a node has a few of its children checked it will be rendered as undetermined, and state will be propagated up. You can also fine tune the cascading options with the cascade config option. Keep in mind when cascading checkbox will check even disabled nodes.

Undetermined state is automatically calculated, but if you are using AJAX and loading on demand and want to render a node as underemined pass "undetermined" : true in its state.